Apparatus for dewatering pulp



APPARATUS FOR DEWATERING PULP Filed April 2, 1964 United States Patent O3,263,598 APPARATUS FOR DEWATERING PULP Klaus Ferdinand Sylla,Sundsvall, Sweden, assignor to Svenska Cellulosa Aktiebolaget,Sundsvall, Sweden Filed Apr. 2, 1964, Ser. No. 356,860

Claims priority, application Sweden, Apr. 3, 1963,

3,670/ 63 2 Claims. (Cl. 100-71) When treating fibrous pulp indewatering presses of the kind comprising two roll-like press memberswhich are provided with perforations or the like and which are adaptedto rotate in a trough or the like for receiving a pulp suspension, theconditions of flow within the trough are highly unsatisfactory becauseof the fact that a more or less immovable plug of pulp of asubstantially higher concentration than that of the supplied pulpsuspension is formed in that zone of the trough located just below theso-called press nip. Parts of such plug get loose and are pulled intothe pressure nip, where they cause an uneven press on the press members.As a result an overpressed pulp and a too hard pressure on the pressmembers will result. This will cause deterioration of the quality of thepulp and a shortened life 'of the press members.

According to the invention, the purpose of which is to eliminate theaforesaid drawbacks in connection with dewatering presses of the kinddescribed, the pulp suspension is supplied to the trough at two, ormore, opposite sides thereof and is caused to flow within the troughtowards that zone of the trough which is located just below the socalledpress nip, where the so-called plug of pulp has a tendency to form. Onepreferred way of carrying out the method consists in supplying the pulpsuspension at a dry content of only 0.5-l.5%, preferably of about 1% orsomewhat less. Hereby the formation of a plug of pulp at that zone ofthe trough which is located just below the press nip will be preventedor counteracted. The dry content of the pulp suspension may also behigher than 1.5% but then there will not be obtained the same effect asthat obtained with the lower dry content. The invention also includesmeans for carrying out the method described.

In the accompanying drawing the method is illustrated in connection witha diagrammatically shown apparatus.

The apparatus comprises two cooperating, substantially horizontal sheetmetal cylinders 1, 2, which are provided with perforations or the like.The sheet metal cylinders are adapted `to rotate in la closed presstrough 3 and their lower portions are adapted to move .in a pulpsuspension, which is supplied to the trough in such a manner that thesuspension will be under a certain pressure within the trough. Uponrotation of the cylinders 1, 2 in the directions -of the arrows each ofthe cylinders will take up a layer of pulp (not shown in the drawing),which during its upward movement is, by means of the cylinders, pressedtogether with the other layer of pulp to form one single web of pulp.The liquid, which is then squeezed away, can ilow through theperforations into the interior of each cylinder, from where it is ledaway at one or both ends of the cylinder.

At two, or more, opposite sides the trough 3 is provided with inlets 4,S for the pulp suspension, which is supplied at a dry content of onlyabout 1%, or somewhat lower, if desired, in order to counteract theformation of an inconvenient plug below the press nip. Moreover, thelower portion of the trough is shaped in such a manner that the enteringpulp suspension will, from each inlet, be directed towards the zonelocated just below the press nip and move the shortest way possible fromsaid inlets to said zone, because between the cylinders 1, 2 and thelower portion of the trough there are provided two passages 6,

3,263,598 Patented ugust 2, 1966 ICC 7, leading from the inlets to thezone located below the press nip. The cross sectional area of saidpassages decreases successively towards said zone, where the trough 3 isprovided with an unobstructed outlet 8 for leading away a partial ow ofthe pulp suspension, such partial flow carrying away lumps of pulp whichare of a higher dry content than that of the rest of the suspension andwhich get detached from the cylinders 1, 2. The trough 3 may also beprovided with a pipe line 9 for supplying air, or some other gas, at thezone located just below the press nip in order to further counteractinconvenient lump formations and to provide for a tighter and moreuniform web of pulp having a lower water content already prior to theweb of pulp entering the press nip.

The described method with the combined effect of the low dry content,the lateral inlets for the pulp suspension, the bottom outlet for apartial llow of the pulp suspension and the supply of air at the zonelocated below the press nip prov-ide for an extraordinarily even web ofpulp. It is possible, therefore, to use the apparatus in question as awet machine, the web of pulp formed between the cylinders being eitherrolled or also pressed to bales. In the latter case the web of materialmay either be cut or folded before being pressed to bales. It ispossible also to use the apparatus in question for the manufacture ofber board.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. Apparatus for dewateri-ng fibrous pulp comprising a trough having abottom and side walls, two parallel, substantially horizontallydisposed, contiguous, roll-like, perforated press members mounted torotate with at least their lower portions within said trough but spacedfrom the bottom and sides thereof, means in said side walls of saidtrough for supplying pulp thereto in quantity sufcient to maintain abody thereof in said trough with its upper surface in contact with saidmembers and an outlet in the bottom of said trough positioned verticallybelow the nip of said members and unobstructed relative to the nip ofsaid members with respect to large-size pulp plugs and particles.

2. Apparatus for dewatering fibrous pulp comprising a trough having abottom and side walls, two parallel, substantially horizontally disposedcontiguous, roll-like perforated press members mounted to rotate with atleast their lower portions within said trough but spaced from the bottomand sides thereof, means in said side walls of said trough for supplyingpulp thereto in quantity suiicient to maintain a body thereof in saidtrough with its upper surface in contact with said members, an outlet inthe bottom of said trough positioned vertically below and unobstructedrelative to the nip of said members, and means for introducing a streamof gas int-o said trough iat a location just below said nip.

References Cited by the Examiner UNITED STATES PATENTS 2,807,998 10/1957Stephan 100-121 3,114,309 12/1963 Haug 100-121X FOREIGN PATENTS LOUIS O.MAASSEL, Primary Examiner.

WALTER A. SCHEEL, Examiner.

1. APPARATUS FOR DEWATERING FIBROUS PULP COMPRISING A TROUGH HAVING ABOTTOM AND SIDE WALLS, TWO PARALLEL, SUBSTANTIALLY HORIZONTALLYDISPOSED, CONTIGUOUS, ROLL-LIKE, PERFORATED PRESS MEMBERS MOUNTED TOROTATE WITH AT LEAST THEIR LOWER PORTIONS WITHIN SAID TROUGH BUT SPACEDFROM THE BOTTOM AND SIDES THEREOF, MEANS IN SAID SIDE WALLS OF SAIDTROUGH FOR SUPPLYING PULP THERETO IN QUANTITY SUFFICIENT TO MAINTAIN ABODY THEREOF IN SAID TROUGH WITH ITS UPPER SURFACE IN CONTACT WITH SAIDMEMBERS AND AN OUTLET IN THE BOTTOM OF SAID TROUGH POSITIONED VERTICALLYBELOW